Within the field of wireless systems, such as, for example, wireless communications systems, a so called primary user is a user who has a license from a regulator to operate within a frequency spectrum within a defined geographical area. A primary user may have some unused parts of his licensed frequency spectrum. The same regulator who grants licenses to primary users may also allow unlicensed usage of primary users' unused parts of the spectrum, or of the licensed parts of the spectrum outside of the defined geographical boundary, so called “secondary usage”. Such “secondary usage” has gained increased interest due to spectrum scarcity, and is often carried out on a so called opportunistic basis, i.e. basically a “first come, first serve” principle.
An issue in secondary usage of an available frequency spectrum is how to distribute the available frequency spectrum between secondary users. This has to be done while respecting the principle that all secondary users have equal rights in the available frequency spectrum. In this context, another issue to be addressed is how a new secondary user in the system could/should inform current secondary user or users about its intention to use the frequency spectrum. Moreover, current secondary user or users of the spectrum can be of completely different system or systems, which means that there may not be any available method of communication between the systems, i.e. between the current secondary users and new users wishing to operate in the frequency spectrum on a secondary basis.